The invention generally relates to seat belt retractors and more particularly to a seat belt retractor having a molded frame with various integrally formed features.
The typical seat belt retractor comprises a metal, load-bearing frame. The frame, at least in the vicinity of the retractor spool or shaft, has a U-shaped body. The frame will also include an upper and lower extension, which are used to attach the retractor to a mounting surface(s). The sides of the U-shaped body are almost universally held together by separate tie bars, cross pieces or struts that span the opposite sides of the frame. Each side of the frame includes an opening that serves as a bushing for the retractor spool or shaft or a separate bushing can be inserted in each opening. Typically, a separate spring housing or spring cassette is attached to one side of the frame. The spring housing encloses a rewind spring, which rewinds the seat belt onto the retractor spool. The center of the spring drives the spool or shaft of the retractor. The other frame side supports the various control mechanisms used to initiate the lock-up of the retractor in an emergency. These control mechanisms include initial sensors such as the vehicle sensor and web sensor, which are located within a separate mechanism housing that is attached to this other frame side. Depending on the design of the retractor, the mechanism housing may also enclose a lock dog (or lock pawl) and an associated lock wheel. The spring housing and mechanism housing are typically made of plastic and secured using snap features or other connectors, in a known manner, to a corresponding frame side. As is also known in the art, the spring housing and mechanism housings are formed with many openings. One disadvantage of this type of construction is that dirt, dust and liquids can easily flow through these openings into these housings, as well as other openings in the frame, and contaminate the spring, sensors and other parts of the retractor. As can be appreciated, moisture easily enters the housings and affects the parts therein. Further, the use of the above-mentioned tie bars, cross pieces or struts and other separate components, including the separately attached spring and mechanism housings, mounting members, and frame parts, increases the parts count, lowers the reliability of the product, increases the possibility of incorrect assembly, and complicates the assembly process. As can be appreciated, an increased number of separate parts in the retractor will increase the overall cost and weight of the retractor.
The present invention reduces part count, increases dimensional control and lessens dimensional variation within a retractor, which provides for improved performance and reliability. Additionally, by using various features that are integrally and simultaneously formed as part of the frame, the orientation of the individual components can be more closely controlled. Additionally, by forming the retractor with many integrally formed elements, the need to mistake-proof the manufacturing process is eliminated (as these features are automatically and properly oriented in the integrally formed frame).
A key criterion used to measure the performance of any seat belt retractor is the degree of noise, buzz or rattle produced. The importance of having a quiet seat belt retractor is magnified if the retractor is installed in a seat and positioned near the top of the seat. As can be appreciated, this mounting location places the retractor in close proximity to the occupant""s ear, making it more difficult to muffle any noise. Further, the use of a metal frame (which is not the case with the preferred embodiment of the invention), as known in the prior art, serves to amplify noise.
It is an object of the present invention to reduce the number of discrete parts used in the manufacture and assembly of a seat belt retractor. An added object of the invention is to provide a retractor that has improved resistance to dust, corrosion and moisture. A further object of the present invention is to manufacture a seat belt retractor that includes a fiber reinforced, resin (or plastic) molded or cast frame. An additional object is to integrally mold, as part of the frame, a number of the secondary retractor components such as part of a spring and a mechanism housing.
A further object of the present invention is to provide a seat belt retractor with a reinforced resin or plastic frame that is capable of withstanding and exceeding the 1136 Kg (2,500 pound) empty spool, pull test defined in FMVSS 209.
Accordingly the invention comprises: a seat belt retractor characterized by good dust, corrosion and moisture resistance, as well as low operating noise. The retractor comprising: an integrally formed, main body portion and at least one integral mounting member. In the preferred embodiment of the invention, the frame is molded using a fiber reinforced plastic or resin having glass fibers in excess of 10 millimeters in length and/or a glass content by weight of more than 50% with an average net length of more than 2000 microns. The main body can optionally include a spring housing wall and mechanism housing wall. An integrally formed spring retainer is used to hold the outer end of a rewind spring. The mechanism side of the frame further includes an integrally formed post or pin to pivotally support a lock pawl. The integrally formed post is permitted to flex under the normal loads achieved during retractor lock-up during an accident. The frame further includes a mechanism stop, which receives a portion of the lock pawl as the post flexes. This stop prevents excessive motion of the post and is also helpful to distribute locking reaction forces across various portions of the frame.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.